Transportable combustible gaseous suspension of solid fuel particles

ABSTRACT

A transportable and combustible gaseous suspension includes solid fuel particles suspended in a gaseous carrier. The solid fuel particles have a sufficiently small particle size so that they remain suspended during transportation. The gaseous carrier may include reactive and inert gases. The solid fuel particles may include coal-derived solid carbonaceous matter. Other examples of solid fuel particles include biomass, refined bioproducts, and combustible polymer particles. The combustible gaseous suspension can be tailored to have an energy density at atmospheric pressure which is comparable to conventional gaseous hydrocarbon fuels. The gaseous combustible fuel may be pressurized to a pressure in the range from 2 to 100 atmospheres.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/443,351, filed Jan. 6, 2017, and entitled COMBUSTIBLE GASEOUSSUSPENSION OF SOLID FUEL PARTICLES. This prior application isincorporated by reference.

BACKGROUND OF THE INVENTION

This disclosure relates to a transportable combustible gaseoussuspension of solid fuel particles. The gaseous suspension includessolid fuel particles suspended in a carrier gas. The gas may be reactivesuch as air, oxygen, mixtures thereof, or the gas may be inert, such asnitrogen. The gaseous suspension of solid fuel particles may beconfigured to have energy characteristics similar to conventionalgaseous hydrocarbon fuels.

BACKGROUND

The energy density of combustible fuels is a measure of the amount ofthermal energy produced by combustion per unit volume. Table 1, below,lists a typical volumetric energy density for four common combustiblegases at normal temperature and pressure (NTP). Normal temperature andpressure is understood to be at 20° C. and 1 atm.

TABLE 1 Volumetric Energy Density of Selected Combustible Gases HeatContent Volumetric Energy Combustible Gas (Btu/lb) Density (Btu/m³)Natural Gas 21,000  37,038 Methane 23,811  35,698 Propane 21,564  89,471Butane 21,640 118,745

It would be an advancement in the art to provide an affordablesubstitute to conventional combustible gases. It would be a furtheradvancement in the art to provide a combustible gas in which thevolumetric energy density can be modified as needed to meet energyrequirements for the combustible gas. It would be a further advancementin the art to provide a combustible gas that is transportable comparableto conventional combustible gases.

SUMMARY OF THE INVENTION

This disclosure relates to a transportable combustible gaseoussuspension of solid fuel particles. The combustible gaseous suspensioncomprises predominantly, by volume, a gaseous carrier in which solidfuel particles are suspended to provide a combustible gas having anenergy density comparable to conventional gaseous hydrocarbon fuels.Non-limiting examples of gaseous hydrocarbons fuels include natural gas,methane, ethane, propane, butane, and gaseous derivatives thereof. Thegaseous carrier may be reactive or inert. Non-limiting examples ofreactive gases include air, oxygen, and mixtures thereof. A non-limitingexample of an inert gas includes nitrogen.

The solid fuel particles have a sufficiently small particle size toremain suspended during transport and use. This is affected by both thedensity of the solid fuel particles and the density of the gaseouscarrier within which the solid fuel particles are suspended. The solidfuel particles will typically have a particles size less than 60 μm, andpreferably less than 40 μm. In some non-limiting embodiments, the solidfuel particles may have a particle size less than 30 μm. In somenon-limiting embodiments, the solid fuel particles have a particle sizeless than 20 μm. The solid fuel particles may have a particle size lessthan 10 μm. The solid fuel particles may have a particle size less than5 μm. In some embodiments, the solid fuel particles have an averageparticle size less than 20 μm. In some non-limiting embodiments, thesolid fuel particles have an average particle size less than 10 μm. Inother non-limiting embodiments, the solid fuel particles have an averageparticles size less than 5 μm. The solid fuel particles may have anaverage particle size less than 2.5 μm.

The solid fuel particles comprise finely-divided particles of anenergetic or combustible fuel material. The solid fuel particles may bederived from a single source of energetic or combustible fuel materialsor a blend or mixture of different energetic or combustible fuelmaterials may be used. In one non-limiting embodiment the solid fuelparticles comprise fine coal particles, including coal-derivedcarbonaceous matter. When coal-derived carbonaceous matter has asufficiently small size to be substantially free of inherent mineralmatter, then it is referred to as coal-derived solid hydrocarbon. Insome embodiments the solid fuel particles comprise coal-derived solidhydrocarbon particles.

In some embodiments, the coal-derived solid carbonaceous matter containsreduced amounts of coal-derived mineral matter and reduced amounts ofsulfur. In one non-limiting embodiment, the coal-derived solidcarbonaceous matter contains less than 1 wt. % coal-derived mineralmatter. In one non-limiting embodiment, the coal-derived solidcarbonaceous matter contains less than 0.5 wt. % sulfur.

The solid fuel particles suspended in the gaseous carrier disclosedherein are sometimes referred to as Micro Clean Carbon Fuel (μCCF).

A dispersant may be used with the coal-derived solid carbonaceous matterto inhibit agglomeration of the fine particles. In one non-limitingembodiment, the dispersant comprises an organic acid. The dispersant maybe an organic acid selected from linear, cyclic, saturated, orunsaturated carboxylic acid and polycarboxylic acids. In one currentlypreferred embodiment, the dispersant is citric acid. In anothernon-limiting embodiment, the dispersant is a lignosulfonate-basedsurfactant. Another dispersant class that may be used include non-ionicdispersants such as polyethylene oxide dispersants.

The solid fuel particles may also be derived from organic materials,including waste organic materials. In still another embodiment, thesolid fuel particles are derived from waste biomass. Further, the solidfuel particles may be a refined bioproduct, such as sugars, starches,cellulose, flour, etc. Even further, the solid fuel particles mayconsist of any naturally occurring or synthesized solid fuel compound,including polymers, e.g. any carbonaceous material.

An object of the invention is to provide a combustible gaseoussuspension of solid fuel particles that has a volumetric energy densitycomparable to that of conventional gaseous hydrocarbon fuels.

In one non-limiting embodiment, the solid fuel particles have a sizeless than 30 μm and an energy density greater than 5000 Btu/lb. Inanother non-limiting embodiment, the solid fuel particles have a sizeless than 30 microns and a density greater than 500 kg/m³. In yetanother non-limiting embodiment, the solid fuel particles have an energydensity greater than 5000 Btu/lb and a density greater than 500 kg/m³.It will be appreciated that solid fuel particle size, energy density,and density values may vary. For example, bituminous coals may have anenergy density on a dry basis in the range from 12,500 to 15,000 Btu/lb,whereas lower rank coals and biosolids may have an energy density on adry basis in the range from 10,000 to 13,000 Btu/lb. Water associatedwith the solid fuel lowers the energy density. Partially oxidized solidfuel particles have a lower energy density compared to non-oxidized fuelparticles.

In one non-limiting embodiment, the gaseous carrier is air, the solidfuel particles comprise coal-derived solid carbonaceous matter and havea particle size less than 10 μm, and the combustible gaseous suspensionof solid fuel particles has a volumetric energy density at atmosphericpressure which is in the range of 25,000 to 120,000 Btu/m³.

In one non-limiting embodiment, the combustible gaseous suspension has apressure in the range from 2 to 100 atmospheres. Pressurization enablesthe combustible gaseous suspension to be transported via pressurized gasdistribution pipelines. In China, for example, natural gas isdistributed at a pressure of about 60 atmospheres. In the United States,natural gas is distributed at a pressure of about 100 atmospheres.

A method of transporting a combustible gaseous suspension may includesuspending solid fuel particles in a gaseous carrier to form acombustible gaseous suspension. The combustible gaseous suspension maybe pressurized to a pressure suitable for transport. Such pressurestypically range from about 60 to 100 atmospheres (atm) for long distancetransportation. Residential gas distribution lines range from about 1 to7 atm (15 to 120 pounds per square inch (psi)). Gas distribution goinginto homes is often regulated down to about 0.25 psi.

In one non-limiting embodiment of the method of transporting acombustible gaseous suspension, the combustible gaseous suspensioncomprises greater than 90 volume % carrier gas and the solid fuelparticles comprise coal-derived solid carbonaceous matter and have aparticle size less than 30 μm.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order that the manner in which the above-recited and other featuresand advantages of the invention are obtained will be readily understood,a more particular description of the invention briefly described abovewill be rendered by reference to specific embodiments thereof that areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 shows a schematic representation of a cyclone used in someexamples to separate solid fuel particles by particle size.

FIG. 2 is a graph of the differential volume by particle diameter of thefine particles that exited the top of the cyclone shown in FIG. 1 andthe larger particles that exited the bottom of the cyclone. FIG. 2 alsoshows the particle size distribution of the coal particles fed into thecyclone.

FIG. 3 shows a schematic representation of a cyclone used in someexamples to separate solid fuel particles by particle size.

FIG. 4 is a graph of the differential volume by particle diameter of thefine particles that exited the top of the cyclone shown in FIG. 3 andthe larger particles that exited the bottom of the cyclone.

DESCRIPTION OF THE INVENTION

This disclosure relates to a combustible gaseous suspension of solidfuel particles. The gaseous suspension of solid fuel particles may beconfigured to have energy characteristics similar to conventionalgaseous hydrocarbon fuels.

Fine solid fuel particles such as fine coal particles can be suspendedin air and transported. This blend of fine solid fuel particles in airbehaves like a combustible gas when transported in pipeline and burnedat the end of use to produce heat and do work. Such a blend used fortransport is a new composition of matter. Table 2 below outlines theweight percent, volume percent, and volumetric energy density forexample blends of fine solid fuel particles suspended in air at normaltemperature and pressure. Fine coal was used as fine solid fuel particlein the results in the table below. The fine coal particles had a densityof 1200 kg/m³ and heat content of 14,500 Btu/lb. Natural gas is the mostcommonly used combustible gas. A blend of 50 wt. % fine solid fuelparticles just described has a volumetric energy density of 39,120Btu/m³, which is similar to natural gas. The volume percent of solidfuel particles at 50 wt. % is 0.1%. As mass and volume percent increase,the volumetric energy content of the combustible gas formed bysuspending fine solid fuel particles in air continues to increase. Ablend of 95 wt. % solid fuel particles only has a volume percent of 1.9%and the volumetric energy density is 729,877 Btu/m³, which is about 20times greater than the volumetric energy content of natural gas atnormal temperature and pressure.

TABLE 2 Combustible gas of air and fine solid fuel particles VolumetricVolume % Energy Density Mass % μCCF μCCF (Btu/m³)  1%    0%   396 10%0.01%   4,351 20% 0.03%   9,787 30% 0.04%  16,775 40% 0.07%  26,089 50%0.10%  39,120 60% 0.15%  58,650 70% 0.24%  91,155 80% 0.41% 156,002 85%0.58% 220,628 90% 0.91% 349,228 95% 1.90% 729,877

The combustible gaseous suspension of solid fuel particles is amulti-phase fuel composition comprising a blend of suspended solid fuelparticles and a gaseous carrier. The gaseous carrier may be reactive orinert. Non-limiting examples of reactive gases include air, oxygen, andmixtures thereof. One non-limiting example of an inert gas is nitrogen.

The solid fuel particles comprise finely-divided particles of anenergetic or combustible fuel material. In one non-limiting embodimentthe solid fuel particles comprise fine coal particles. Morespecifically, the fine coal particles comprise coal-derived carbonaceousmatter. When milled to a sufficiently small size to be substantiallyfree of inherent mineral matter, coal-derived carbonaceous matter existsas coal-derived solid hydrocarbon. In another non-limiting embodimentthe solid fuel particles comprise coal-derived solid hydrocarbonparticles.

In another embodiment the solid fuel particles are derived from organicmaterials, including waste organic materials. In still anotherembodiment, the solid fuel particles are derived from waste biomass.Non-limiting examples of waste biomass include sawdust, plant cuttings,wood chips, and plant stalks. Further, the solid fuel particles may be arefined bioproduct. Non-limiting examples of a refined bioproductinclude sugars, starches, cellulose, flour, etc. Even further, the solidfuel particles may consist of any synthesized solid fuel compound.Non-limiting examples of synthesized solid fuel compounds include whichinclude polymers such as polyethylenes, polypropylenes, polycarbonates,polystyrenes, rubbers, etc. The synthesized solid fuel compounds may bewaste organic materials, including waste polymers. Non-limiting examplesof waste polymers include used tires, polypropylene grocery bags, andStyrofoam.

The solid fuel particles may be derived from a single source ofenergetic or combustible fuel materials. Alternatively, the solid fuelparticles may be derived from a blend or mixture of different energeticor combustible fuel materials.

The solid fuel particles have a size that enables them to be easilysuspended and to remain suspended in the gaseous carrier for a practicalperiod of time during storage, transport, and/or use. Stokes law definesthe frictional force or drag force when the Reynold's number is low(e.g. for very small spherical particles) as it passes through a fluidor gas. When the drag force is set equal to the gravitationalacceleration force, then a terminal velocity can be calculated for thesevery small particles. This case assumes no other forces other than thedrag of calm air. Thus, Stokes Law can be used to calculate the settlingvelocity of a sphere of a given density in air or other gasses orliquids if the diameter is less than about 250 microns:

$V = {\frac{d^{2} \cdot g}{18 \cdot \eta} \cdot \left( {{Ws} - {Wa}} \right)}$

Where d=the geometric diameter of the sphere (m)

Ws=the density of the sphere (kg/m³)

Wa=the density of the air (kg/m³)

g=acceleration due to gravity (m/s²)

η=the viscosity of the fluid (kg/(m*s))

Table 3 shows the calculated settling velocity of spherical particles inair at normal temperature and pressure for diameters from 0.5 microns upto 60 microns when Ws=1200 kg/m³, Wa=1.2 kg/m³, g=9.8 m/s², andη=1.81×10⁻⁵ kg/(m*s) using a model based on Stokes Law.

TABLE 3 diameter Settling Velocity (μm) (m/s) 0.5 9.01 × 10⁻⁶ 1 3.61 ×10⁻⁵ 2.5 2.25 × 10⁻⁴ 5 9.01 × 10⁻⁴ 10 3.61 × 10⁻³ 20 1.44 × 10⁻² 30 3.25× 10⁻² 60 1.19 × 10⁻¹

A gaseous combustible suspension moving at a velocity exceeding thesettling velocity of the particles in suspension will keep the particlessuspended.

From Stokes Law and the foregoing discussion, it will also beappreciated that particles having a lower density will also possess alower settling velocity. It is possible to suspend solid fuel particlesin a gaseous carrier that have a greater particle size and a lowerdensity compared so smaller and denser solid fuel particles. Thus,different types and sizes of solid fuel particles may be suspended andremain suspended in the combustible gaseous fuel.

As noted above, the solid fuel particles should have a particle sizeless than 60 μm, and more preferably less than 40 μm. In onenon-limiting embodiment, the solid fuel particles have a diameter lessthan 30 μm. In another embodiment, the solid fuel particles have adiameter less than 20 μm. In yet another embodiment, the solid fuelparticles have a diameter less than 10 μm. In one embodiment, the solidfuel particles have a diameter less than 5 μm. In some embodiments, thesolid fuel particles have an average particle size less than 20 μm. Insome non-limiting embodiments, the solid fuel particles have an averageparticle size less than 10 μm. In a further embodiment, the solid fuelparticles have an average diameter less than 5 μm. In still anothernon-limiting embodiment, the solid fuel particles have an average sizeless than 2.5 μm. In a non-limiting embodiment, 99% of the solid fuelparticles are less than 40 μm. In one non-limiting embodiment, 99% ofthe solid fuel particles are all less than 20 μm. In anothernon-limiting embodiment, 99% of the solid fuel particles are all lessthan 10 μm. In other non-limiting embodiments, larger size and lowerdensity solid fuel particles may be successfully used.

The time period during which the solid fuel particles remain suspendedmay vary depending upon the intended use of the combustible gaseoussuspension. For example, if the combustible gaseous suspension isprepared on demand for immediate use, then the suspension time periodmay be short, such as seconds, minutes, or hours. In contrast, if thecombustible gaseous suspension is stored for a period of time, then thepractical suspension time period may be measured in days, weeks, ormonths. It will be appreciated that finer sized solid fuel particleswill naturally remain suspended for a longer time period compared tolarger sized solid fuel particles. A particle having a size of about 10μm may remain suspended for minutes to hours, whereas a particle havinga size of about 2.5 μm may remain suspended for days or weeks.

In one disclosed embodiment, the gaseous carrier comprises air and thesuspended solid fuel particles comprise fine coal particles whichinclude coal-derived carbonaceous matter. The amount of coal particlesblended with air may range from about 5 volume % or less, at atmosphericpressure. The coal particles may have an average particle size less than30 μm.

A dispersant may be added to the fine coal particles to reduce particleagglomeration. In one non-limiting embodiment, the dispersant is anorganic acid. The dispersant may be an organic acid selected fromlinear, cyclic, saturated, or unsaturated carboxylic acid andpolycarboxylic acids. In one currently preferred embodiment, thedispersant is citric acid. In another non-limiting embodiment, thedispersant is a lignosulfonate based surfactant. Another dispersantclass that may be used is non-ionic dispersants such as a polyethyleneoxide dispersant.

The following non-limiting examples are given to illustrate severalembodiments relating to the disclosed combustible gaseous suspension ofsolid fuel particles. It is to be understood that these examples areneither comprehensive nor exhaustive of the many types of embodimentswhich can be practiced in accordance with the presently disclosedinvention.

Example 1

An experiment was designed to test whether fine coal particles settle incalm air as predicted by Stokes Law. First, fine coal particles of adefined size were obtained by passing the coal particles through a smallcyclone. Cyclones are devices that can be used to classify particles inflowing water or air based on size.

The cyclone used in this experiment is depicted in FIG. 1. It had abottom opening of about 4.7 mm and a top opening of 14.5 mm and was 105mm tall. A small vacuum pump operating at a rate of 1.9 liters perminute was connected to the top port of the cyclone. Large particlesthat fell out of the bottom port were collected in a cap or grit pot.Small particles carried out of the top of the cyclone in the airstreamwere collected on fine filter paper before entering the vacuum. FIG. 2shows a particle size analysis graph for the smaller particles thatexited the top of the cyclone and the larger particles that exited thebottom of the cyclone. Also shown in FIG. 2 is the particle sizedistribution of the coal particles that fed into the cyclone. The fineparticles exiting the top had an average particles size of 4.4 μm. Thelarge particles exiting the bottom of the cyclone had an averageparticle size of 18.8 μm.

The cyclone was then set up as shown in FIG. 3. In this configuration,the fine particles exiting the cyclone were passed through a stainlesssteel cube box with inside wall lengths of 2.25″ with a 1.5″ diameterwindow on two sides so that one could see through the box and seesuspended particles. The volumetric air flow of the vacuum pump wasmeasured at 1.9 liters per minute. The tubing going from the cyclone tothe steel box and from the steel box to the vacuum pump had a 6.9 mminside diameter. Based on the volumetric air flow rate of the vacuumpump, the air velocity in the tube was calculated to be 0.85 m/s. Theair velocity in the box slows down due to the larger cross-sectionalsurface are of the container and was calculated to be 0.0096 m/s.

According to Table 3, the settling velocity for particles suspended inair of a 60 μm diameter particle is 0.12 m/s, the settling velocity of a30 μm particle is 0.033 m/s, the settling velocity of a 20 μm particleis 0.014 m/s, and the settling velocity of a 10 μm particle is 0.0036m/s. From FIG. 2, some 30 and 60 μm particles are in the feed particles.The air velocity in the tubing is greater than the settling velocity forparticles in this range and thus, they should be able to be transportedin the tubing. However, the air velocity inside the box is lower thanthe settling velocity of these particles. Thus, particles larger than 30microns are not expected to remain in suspension inside the box with thevolumetric air flow rate of this experimental setup.

According to Table 3, the settling velocity of a 10 μm particle is0.0036 m/s. The air velocity inside the box is 0.0096 m/s which isgreater than the settling velocity of 10 μm particles. Thus, particles10 μm and smaller are expected to be in suspension in the box when airis flowing through it at the volumetric rate of 1.9 liters per minute.

When the experimental setup described herein and shown in FIG. 3 wasoperating, the particles exiting the top of the cyclone and travellinginto the box had an average particle size of 4.4 μm. A light shinedthrough the back window of the box. The particles could be observedtraveling in the current of air as it expanded from the volume of thetube entering the box to the volume of the box. As long as the pump wasleft on and particles were being delivered to the cyclone, particlesentered and exited the box without settling to the bottom of the box.

When the pump was turned off, the flow of air stopped. The particlescould then be observed to slowly drift to the bottom of the box. Thetime required for the particles to travel 1 cm was measured to beapproximately 10 seconds, corresponding to a settling velocity of 0.001m/s. This settling velocity matches the calculated settling velocity of0.0009 m/s for a 5 μm diameter particle.

The cyclone was then removed from the experimental setup so that thesuction tube fed the particles into the box. As stated above, any 30 μmand 60 μm particles are expected transport in the tubing but are thenexpected to settle soon after entering the box, based on the calculatedair velocity for the two different cross-sectional areas. Particles inthe size range of about 10 μm in the feed are expected to remainsuspended in the box because the air velocity in the box exceeds theirsettling velocity.

When the feed was introduced directly into the box by removing thecyclone from the experimental setup, a higher density of particles wasvisually observed in the box. When the vacuum pump was shut off and airvelocity went to zero, the particles were observed to settle morequickly indicating a population of larger diameter particles. The timerequired for the particles to travel 1 cm was measured to beapproximately 0.8 seconds, corresponding to a settling velocity of 0.012m/s. The air velocity inside the box calculated from the volumetric flowrate and the cross-sectional area was calculated to be 0.0096 m/s, whichis slightly lower than the measured settling rate of 0.012 m/s. Thevisual method for measuring settling rate may not be accurate enough.However, the fact that the two rates are on the same order and so closeto one another validates the assumption that air velocity greater thanthe settling rate of a particle will keep that particle in suspension ina flowing gas. The settling velocity for a 10 μm diameter particle wascalculated to be 0.0036 m/s. Thus, the particles must be larger than 10μm and smaller than 30 μm on average. In fact, a particle with adiameter of 18.25 μm would have a settling velocity in air at normalpressure and temperature of 0.012 m/s.

Example 2

A larger cyclone was used as part of a powder capture system. The largeand small dimensions of the cone were 27.5 cm and 7.3 cm, respectively.The cyclone was 61 cm tall. FIG. 4 shows a graph of the differentialvolume by particle diameter of the large particles exiting the smallopening at the bottom of the cyclone and the small particles carriedwith the airstream exiting the top of the cyclone. The average particlesizes were 21.4 μm and 6.2 μm respectively. Note that the largerparticles were the feedstock used for the experiment with the smallcyclone discussed in Example 1, above. The fine particles with anaverage particle size were transported in metal ducting over 50 feetaway without significant sedimentation to the sidewalls of the ducting.Once the ducting was coated with a thin film of fine particles due tostatic charges, losses were negligible.

The described embodiments and examples are all to be considered in everyrespect as illustrative only, and not as being restrictive. The scope ofthe invention is, therefore, indicated by the appended claims, ratherthan by the foregoing description. All changes that come within themeaning and range of equivalency of the claims are to be embraced withintheir scope.

The invention claimed is:
 1. A transportable combustible gaseoussuspension comprising: a non-combustible gaseous carrier; and solid fuelparticles suspended in the gaseous carrier, wherein the solid fuelparticles consist of particles of coal-derived solid carbonaceous matterhaving a particle size less than 40 μm.
 2. The transportable combustiblegaseous suspension according to claim 1, wherein the gaseous carrier isselected from air, oxygen, and mixtures thereof.
 3. The transportablecombustible gaseous suspension according to claim 1, wherein the solidfuel particles have a heat content greater than 5000 BTU/lb.
 4. Thetransportable combustible gaseous suspension according to claim 1,wherein the solid fuel particles have a density greater than 500 kg/m³.5. The transportable combustible gaseous suspension according to claim1, wherein the solid fuel particles have a heat content greater than5000 BTU/lb and a density greater than 500 kg/m³.
 6. The transportablecombustible gaseous suspension according to claim 1, further comprisinga dispersant associated with the coal-derived solid carbonaceous matter.7. The transportable combustible gaseous suspension according to claim6, wherein the dispersant comprises an organic acid.
 8. Thetransportable combustible gaseous suspension according to claim 7,wherein the dispersant is citric acid.
 9. The transportable combustiblegaseous suspension according to claim 7, wherein the dispersant isselected from linear, cyclic, saturated, or unsaturated carboxylic acidand polycarboxylic acids.
 10. The transportable combustible gaseoussuspension according to claim 1, wherein the solid fuel particles havean average particle size less than 30 μm.
 11. The transportablecombustible gaseous suspension according to claim 1, wherein the solidfuel particles have a particle size less than 20 μm.
 12. Thetransportable combustible gaseous suspension according to claim 1,wherein the solid fuel particles have a particle size less than 10 μm.13. The transportable combustible gaseous suspension according to claim1, wherein the solid fuel particles have a particle size less than 5 μm.14. The transportable combustible gaseous suspension according to claim1, wherein the combustible gaseous suspension has a pressure in therange from 2 to 100 atmospheres.
 15. The transportable combustiblegaseous suspension according to claim 1, wherein the solid fuelparticles have a particle size less than 10 μm and the quantity of solidfuel particles is selected to provide the transportable combustiblegaseous suspension with a volumetric energy density in the range of25,000 to 120,000 Btu/m³.
 16. A method of transporting a combustiblegaseous suspension comprising: suspending solid fuel particles in anon-combustible gaseous carrier to form a combustible gaseoussuspension, wherein the solid fuel particles consist of particles ofcoal-derived solid carbonaceous matter having a particle size less than40 μm; and pressurizing the combustible gaseous suspension to a pressuresuitable for transport in the range from about 2 to 100 atmospheres,wherein the solid fuel particles have a sufficiently small size toenable them to remain suspended in the gaseous carrier during transport.17. The method of transporting a combustible gaseous suspensionaccording to claim 16, wherein the solid fuel particles consist ofparticles of coal-derived solid carbonaceous matter having a particlesize less than 20 μm.
 18. The method of transporting a combustiblegaseous suspension according to claim 16, wherein the solid fuelparticles remain suspended in the gaseous carrier during transport via apressurized natural gas distribution pipeline.
 19. A method oftransporting a combustible gaseous suspension comprising: suspendingsolid fuel particles in a non-combustible gaseous carrier to form acombustible gaseous suspension, wherein the solid fuel particles consistof particles of coal-derived solid carbonaceous matter having a particlesize less than 40 μm; and flowing the combustible gaseous suspensionthrough a gaseous fuel distribution pipeline at a velocity exceeding asettling velocity of the solid fuel particles.
 20. The method oftransporting a combustible gaseous suspension according to claim 19,wherein the solid fuel particles have an average particle size less than30 μm and the velocity exceeds 3.25×10⁻² m/s.